Watch for a developing Pacific jet
An intense baroclinic system is in the process of developing near Japan. It will contribute to an anticipated pattern change as a ridge develops near ~145W and a downstream trough digs over the western USA. A few of the PSD ensemble members from today (5 of 15) have the trough slightly further west but the majority of the models are consistent with yesterday's forecasts. The trough should set up over the western USA. Cold temperatures can be expected over the west, including the California region. The next stage in the atmosphere's evolution would be for the west Pacific jet to continue to intensify and start to shift east across the basin. The MJO component of this process can be seen in this forecast from Matt Wheeler:
As these forecasts suggest, the timing for west coast impacts would be beyond 15 January. This is consistent with Ed's discussion from yesterday where he also speculated on the synoptic details of how west coast impacts may occur. Presently none of the models show a strong jet in place in the extended range. The EC and NCEP ensembles have a feeble 500 mb low anomaly east of the dateline by day 11. It's a good bet that the models are underpredicting the jet intensification. A more detailed analysis of the weather-climate situation after 15 January will be posted on Monday.